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INTRODUCTION
Since the dawn of civilization, humans have transformed the environment
to accommodate and satisfy their needs. Advances in agriculture, mining,
manufacturing, transportation, and energy production, for example, have
dramatically improved standards of living over the centuries. However, this progress
has been achieved at a cost to Earthâs natural systems and has yet to be more
equitably distributed to all. Human impacts on the environment accelerated with
the advent of the Industrial Age and the subsequent rapid growth of the human
population, creating significant areas of friction between human societies and the
environment. At its worst, the human presence is manifest in pollution hanging over
cities; sprawling development in place of forests; hazardous chemicals permeating
rivers, lakes, and soil; vanishing species; and a changing climate.
The field of environmental engineering emerged to support human and
environmental needs while mitigating adverse impacts associated with human
activities. Propelled by public sentiment in support of protecting natural resources
and human health and by laws aimed at curtailing some of the most egregious
forms of environmental damage, the field has achieved remarkable successes over
the past several decades. However, the solutions of the past will not be sufficient
to address the problems of the future. As humanity faces mounting and diverse
challenges, the field of environmental engineering must build on its unique
strengths, inspire and implement visionary solutions, and continue to evolve in
order to serve the best interests of people and the planet.
What is Environmental Engineering?
Environmental engineering is best characterized by the vast array of issues that
its practitioners address. Broadly, environmental engineers design systems and
solutions at the interface between humans and the environment. Historically, this
work focused on the provision of water and treatment of wastewater, drawing upon
the fieldâs roots in sanitation system design and public health protection. In the
1970s the term environmental engineering replaced the previous term, sanitary
engineering, as the fieldâs focus broadened to include the mitigation of pollution
in air, water, and soil. Around the same time, the fieldâs approach to design shifted
from a focus on engineered treatment systems toward a greater emphasis on
ecological principles and processes. More recently, the field has expanded further
to address emerging contaminants, chemical exposures from goods and materials,
and endeavors such as green manufacturing and sustainable urban design.
To support these activities, many environmental engineers have acquired expertise
in a wide variety of domains, including hydrology, microbiology, chemistry,
systems design, and civic infrastructure. About half of practicing environmental
engineers have graduate degrees; practitioners apply their craft to a wide range of
Introductionâ |â 1

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areas in industry, government, nonprofits,
and academia. Trained to take a systems-
level approach to problems, environmental
engineers often act as a bridge among
scientists, other engineers, decision makers,
and communities to assess options, weigh
trade-offs, and design cost-effective,
pragmatic solutions.
The discipline of environmental engineering
has no single, widely agreed-upon definition.
This report does not focus on defining the field
as it is, but rather seeks to outline a vision for
the ways in which environmental engineering
expertise, skills, and areas of focus can help
address future challenges. Fulfilling this vision
will require a new model for environmental
engineering practice, education, and researchâ
building on and complementary with the fieldâs traditional core competenciesâas
outlined in the reportâs final chapter.
New Pressures in the 21st Century
In this century, human pressure on the environment will accelerate. Life expectancy
has increased substantially across the globe over the past several decades as living
conditions have improved and is projected to continue to increase.5 The United
Nations predicts that by 2050 the worldâs population will reach roughly 9.8
billion people, an increase of approximately 30 percent from today.6 As human
BUILDING ON A REMARKABLE LEGACY
Although the term environmental engineering has been in use crises sparked the creation of new laws aimed at preventing
for only a few decades, the fieldâs roots reach back centuries. and mitigating pollution in air, water, and soil. After Londonâs
Romans built sophisticated sewage disposal and water supply Great Smog of 1952 killed thousands of people, the Parliament
systems, some of which still deliver water to Rome today. In of the United Kingdom passed the first major legislation aimed
the new world, the Inca and the Maya developed innovative at limiting emissions from households and industries. In the
systems to distribute clean water to great cities such as Cusco United States, debilitating smog over Los Angeles and other
and Tikal. The beginnings of modern-day environmental
engineering are typically traced to the creation of the
first municipal drinking water filtration systems, the first
continuously pressurized drinking water supply, and the first
large-scale municipal sanitary sewer in 19th century London.
These and subsequent advancements markedly improved
peopleâs quality of life by curbing the spread of disease. In
the early 20th century, chlorine-based disinfection for water
treatment and advances in wastewater treatment contributed
to a drastic decline in urban mortality rates.1
Environmental engineering continued to evolve
throughout the 20th century as a series of environmental
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populations grow, so too will humanityâs demand for natural resources and impacts
on natural systems. These impacts will play out in different ways in different areas.
At least two-thirds of the population in 2050 will live in cities, compounding
pressures on urban systems that provide clean water, food, energy, and sanitation.
Rapid economic and population growth in lower-income countries threatens to
overwhelm basic infrastructure and drive sharp increases in pollution, just as the
developed world experienced in the early 20th century. At the same time, countries
of all income levels face new types of challengesâmany driven by climate
changeâthat existing policies, technologies, and infrastructures are not equipped
to handle.
Most environmental engineering expertise is concentrated in developed countries,
but some of the most vexing challenges are concentrated in the worldâs poorer
regions. More than 10 percent of humanity continue to live off less than $1.90
per day and lack access to basic services and economic opportunity.7 More than
2 billion people still lack access to basic sanitation services,8 more than 1 billion
are without electricity,9 and more than 3 billion people rely on household energy
sources that produce dangerous indoor air pollutants.10 Unsafe air and water
rank among the major contributors to disease and death worldwide.11 Despite
economic progress, meeting the basic human needs of the large swath of the
worldâs population who live in extreme poverty will remain a monumental task in
the decades ahead.
At the same time, many more people are experiencing an improved standard of
living. The proportion of people living in extreme poverty has been reduced by
half since 1990.12 Recent economic growth in China, Brazil, and India has been
lifting about 150 million people out of poverty and into the middle class each
year.13 Although undoubtedly positive for peopleâs well-being and quality of life,
this growth also has the potential to create or exacerbate some of the same types
U.S. cities from vehicle emissions led to the passage of the with new analytical methods and modeling tools to quantify
Clean Air Act of 1970. Environmental engineers, working with and reduce contamination of rivers and streams.
atmospheric chemists and other scientists, responded by Another infamous episode focused the public and
developing models of pollution and its sources, monitoring environmental engineers on contamination of soils and
emissions, helping ensure compliance with regulations, groundwater. More than 21,000 tons of hazardous chemicals
and designing and implementing technologies to improve dumped into a 70-acre industrial landfill near Love Canal,
air quality. Such efforts resulted in a two-thirds drop in U.S. New York, during the 1950s and 1960s seeped into waterways
emissions of common air pollutants between 1970 and 2017. 2 and soil, affecting the health of hundreds of residents. 3
The same period saw a major movement to reduce water Responding to the disaster, Congress in 1980 passed a law
pollution. After the 1969 fire on Ohioâs Cuyahoga River called launching the Superfund program, which called on the U.S.
public attention to the widespread practice of dumping Environmental Protection Agency to develop remedial actions
industrial and household wastes into rivers and streams, the and treatment technologies to reduce pollutants at designated
U.S. Clean Water Act of 1972 banned the discharge of pollutants sites.4 Environmental engineers today play a crucial role in
from pipes and other point sources into navigable waters carrying out this charge by providing technical expertise to
without a permit. In 1974, Congress passed the Safe Drinking assess and remediate existing contaminants and by designing
Water Act establishing standards for public water systems. new processes and disposal methods to prevent future
Environmental engineers work to support the enforcement of contamination.
these laws by developing water treatment technologies along
Introductionâ |â 3

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of environmental problems that wealthier countries have
SUSTAINABLE DEVELOPMENT GOALS grappled with in the past. Some mistakes of the past may
A vision for responsibly improving quality of be avoided with the benefit of hindsight, public awareness,
life in the worldâs poorer regions is embodied and new technology. Nonetheless, it is expected that
in the United Nationsâ 2030 Agenda for increased purchasing power and consumption preferences
Sustainable Development, which articulates of the worldâs growing middle class will generally lead
17 strategic goals designed âto end poverty, to increases in resource and energy use, with negative
protect the planet, and ensure prosperity for implications for ecosystems, biodiversity, and human
all.â14 While environmental quality has the health. The United Nationsâ Sustainable Development
potential to contribute to all of these goals, at Goals offer a framework to guide economic development
least 10 of them relate directly or indirectly to while minimizing its potential downsides (see sidebar). The
the work of environmental engineers: grand challenges for environmental engineers outlined in
this report align closely with many of these goals.
Goal 2: Zero Hunger
Goal 3: Good Health and Well-Being In addition to drivers related to population growth,
Goal 6: Clean Water and Sanitation urbanization, poverty, and economic development, climate
Goal 7: Affordable and Clean Energy change adds new complexity to nearly every environmental
Goal 9: Industry, Innovation, and challenge. Expected increases in extreme weather, including
âInfrastructure heat waves, drought, hurricanes, wildfires, and floods place
Goal 11: Sustainable Cities and Communities enormous strain on water supplies, agriculture, and the
Goal 12: Responsible Consumption and built environment. Global warming is already contributing
Production to the reemergence of pathogens and spread of insect
Goal 13: Climate Action borne diseases to new regions. For the increasing number
Goal 14: Life Below Water of people living near a coast, sea-level rise combined with
Goal 15: Life on Land storm surge has become a threat to life and property. These
trends pose urgent threats in developing and developed
countries alike.
A New Vision for Environmental Engineering
Environmental engineers were instrumental in pulling the United States and
other countries out of the depths of environmental crises such as Love Canal
and urban smog. Rivers in Ohio no longer catch fire. Cholera and other
once-prevalent waterborne diseases are now so rare in the United States that
lightning strikes pose a greater threat. These successes, worthy of celebration,
reflect the value of the fieldâs approach to creating systems and solutions that
are grounded in sound scientific, ecological, and engineering principles while
being cost-effective, feasible, and acceptable for the many stakeholders that
environmental engineers serve.
But these battles are not over. Pollution and waterborne diseases persist around
the globe. Rivers are still catching fire. Billions of people suffer from inadequate
access to clean water, food, sanitation, and energy. As the human population
continues to grow, demands intensify and humanityâs mark on the planet
deepens. In short, the challenges ahead are of a different nature and a larger scale
than those faced in the past.
4â ENVIRONMENTAL ENGINEERING IN THE 21st CENTURY:â ADDRESSING THE GRAND CHALLENGES
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Todayâs environmental engineers also operate in a different policy context than the
one that fueled past achievements. The types of sweeping laws that directed public
attention and funding toward large-scale infrastructure expansion, basic research,
and technology development for environmental remediation in the 1970s-1990s
have not emerged to address todayâs national and global challenges. Legislation
may not be the primary drivers of future innovation.
As we face this period of dramatic growth and change, it is time to step back and
consider new roles that environmental engineers might play in meeting human
and environmental needs. Although efforts to characterize, manage, and remediate
existing environmental problems are still essential, environmental engineers
must also turn their skills and knowledge toward the design, development, and
communication of innovative solutions that avoid or reduce environmental
problems. The core competencies of environmental engineering, which emphasize
not only specific goals related to human needs and the condition of the environment
but holistic consideration of the consequences of our actions, are uniquely valuable
in developing the solutions that will be needed in the coming decades.
Introductionâ |â 5

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The report identifies five pressing challenges for the 21st century that environmental
engineers are uniquely poised to help advance:
1: Sustainably supply food, water, and energy
2: Curb climate change and adapt to its impacts
3: Design a future without pollution and waste
4: Create efficient, healthy, resilient cities
5: Foster informed decisions and actions
These grand challenges stem from a vision of a future world
where humans and ecosystems thrive together. Although this
is unquestionably an ambitious vision, it is feasibleâand
imperativeâto achieve significant steps toward these challenges
in both the near and long term.
â â
â The challenges provide focal points for evolving environmental
engineering education, research, and practice toward increased
â â contributions and a greater impact. Implementing this new
model will require modifications in the educational curriculum
and creative approaches to foster interdisciplinary research on
complex social and environmental problems. It will also require
broader coalitions of scholars and practitioners from different
disciplines and backgrounds, as well as true partnerships
with communities and stakeholders. Greater collaboration with economists,
policy scholars, and businesses and entrepreneurs is needed to understand and
manage issues that cut across sectors. Finally, this work must be carried out with
a keen awareness of the needs of people who have historically been excluded
from environmental decision making, such as those who are socioeconomically
disadvantaged, members of underrepresented groups, or those otherwise
marginalized.
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The inevitable challenges we will face over the next 30 to 50 years are daunting,
but a better future is possible. By learning from the past, capitalizing on existing
knowledge and skills, and growing into new roles, environmental engineers have
the power to engineer a healthier and more resilient world.
INSPIRED BY ENGINEERING GRAND CHALLENGES
This report was inspired in part by the National Academy of Engineeringâs Grand Challenges for Engineering, announced in
2008. The effort is aimed at inspiring young engineers across the globe to address the biggest challenges facing humanity
in the 21st century. An international group of leading technological thinkers identified 14 challenges within the crosscutting
themes of sustainability, health, security, and joy of living. Seven of those challenges (in green) require significant input
from environmental engineers.
Advance Personalized Learning Secure Cyperspace
Make Solar Energy Economical Provide Access to Clean Water
Enhance Virtual Reality Provide Energy from Fusion
Reverse-Engineer the Brain Prevent Nuclear Terror
Engineer Better Medicines Manage the Nitrogen Cycle
Advance Health Informatics Develop Carbon Sequestration Methods
Restore and Improve Urban Infrastructure Engineer the Tools of Scientific Discovery
Introductionâ |â 7

Environmental engineers support the well-being of people and the planet in areas where the two intersect. Over the decades the field has improved countless lives through innovative systems for delivering water, treating waste, and preventing and remediating pollution in air, water, and soil. These achievements are a testament to the multidisciplinary, pragmatic, systems-oriented approach that characterizes environmental engineering.

Environmental Engineering for the 21st Century: Addressing Grand Challenges outlines the crucial role for environmental engineers in this period of dramatic growth and change. The report identifies five pressing challenges of the 21st century that environmental engineers are uniquely poised to help advance: sustainably supply food, water, and energy; curb climate change and adapt to its impacts; design a future without pollution and waste; create efficient, healthy, resilient cities; and foster informed decisions and actions.

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